1. Field of the Invention
The present invention relates to a method and apparatus for displaying an image signal such as a television signal, and more particularly to an image displaying method and apparatus capable of displaying an image at a high luminance.
2. Related Background Art
One horizontal period of a television signal has a horizontal image signal period and a horizontal blanking period. A scanning system for such image signals has generally a horizontal scanning time of 50 xcexcsec and a horizontal blanking time of 12.7 xcexcsec. Therefore, the period during which a beam is applied to each picture element (pixel) in one scan line is the period derived by dividing the horizontal scanning time by the number of pixels. For example, if one scan line has 500 pixels, the period is 100 nsec (=50 xcexcsec/500).
In a conventional image displaying method, the time while an electron beam is applied to each pixel is very short. Accordingly, a very high beam energy is required to obtain a certain level of satisfactory luminance.
In order to solve this problem, techniques are disclosed in Japanese Patent Publication No. 61-26271 in which one horizontal scanning period of an image signal is divided into a plurality of periods, and the image signals in each period are processed in parallel to prolong the supply time of an electron beam to each pixel and to increase the luminance.
Specifically, as shown in FIG. 9, one horizontal scanning period (TH) is divided into five periods each having a time equal to the horizontal blanking time (TBLK). Of these five periods, the four periods are effective display periods of image signals. Target pixels in the horizontal direction are divided into four groups of pixels and electron beams are sequentially supplied to the pixels in each group.
With this method described in Japanese Patent Publication No. 61-26271, image signals in each divided group cannot be converted into parallel signals unless all image signals in the divided group are read. Therefore, the parallel signals converted from image signals in each divided period are output and displayed during the next divided period. Specifically, the image signals corresponding to the periods T1, T2, T3 and T4 are converted into parallel signals and output and displayed at the same time during the first to fourth quarter division periods of a target scan line.
With this method, however, although the image signals corresponding to the period T4 can be displayed by utilizing the period corresponding to the period TBLK, the image signals cannot be displayed during the period corresponding to the period T1 after the period TBLK, because no image signals exist during this period TBLK. Therefore, only one fifth of one horizontal scanning time TH is used for displaying image signals and it can be said that the method is unsatisfactory from the viewpoint of high luminance.
It is an object of the invention to provide an image displaying method and apparatus capable of solving the above-described technical problem and displaying an image at a high luminance.
In order to achieve the above object, the invention provides an image displaying method of displaying an image signal having a horizontal image signal period and a horizontal blanking period, the method comprising the steps of: (a) writing a first horizontal line image signal in a write memory; (b) reading in parallel the first horizontal line image signal from a read memory during a horizontal blanking period next to the horizontal image signal period; (c) amplifying the first horizontal line image signal to thereafter perform modulation; (d) displaying the first horizontal line image signal at least until a next horizontal image signal line period terminates; and (e) sequentially repeating the steps (a) to (d) to scan horizontal lines.
According to another aspect of the invention, there is provided an image display apparatus for displaying an image signal, comprising: a linear optical deflector having optical deflectors for pixels in a horizontal direction, one horizontal line image signal being displayed at the same time by modulating in parallel the linear optical deflector.